Secondary battery and method of fabricating the same

ABSTRACT

A secondary battery includes an electrode assembly and a can having an opening at one end of the can. The electrode assembly is housed in the can. A cap plate seals the opening. The cap plate includes an electrolyte injection hole. An electrode terminal is coupled to the cap plate electrical connecting the electrode terminal and the electrode assembly. A gasket is located between the electrode terminal and the cap plate to insulate the electrode terminal from the cap plate. A plug seals the electrolyte injection hole, the plug being coated with an elastic film.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of Korean PatentApplication No. 10-2006-0027521, filed on Mar. 27, 2006, in the KoreanIntellectual Property Office, the entire content of which isincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a secondary battery, and moreparticularly to a secondary battery having an improved electrolytecontainment structure.

2. Discussion of Related Art

Secondary batteries are rechargeable as opposed to primary batterieswhich are not rechargeable. Secondary batteries are used in electronicdevices such as cellular phones, laptop computers, and camcorders.Lithium secondary batteries have high energy density unit per weight andsupply 3.6 V of power, three times greater than nickel-cadmium batteriesor nickel-hydrogen batteries.

Lithium secondary batteries use lithium oxide as a cathode electrodeactive material and carbon materials as anode electrode activematerials. Generally, lithium secondary batteries are classified asliquid electrolyte batteries (lithium ion batteries) and high moleculeelectrolyte batteries (lithium polymer batteries) depending on the typeof electrolyte used. Also, lithium secondary batteries may also beclassified by their housing, such as cylinder types, square types, andpouch types.

FIG. 1 shows a sectional view of a conventional square type secondarybattery 10. As illustrated in FIG. 1, the secondary battery 10 includesa can 11 housing an electrode assembly 12, and a cap assembly 20 sealingthe can 11.

The electrode assembly 12 includes a cathode electrode plate 13, aseparator 14 and an anode electrode plate 15. A cathode electrode tap 16and an anode electrode tap 17 protrude from the cathode electrode plate13 and the anode electrode plate 15, respectively.

The cap assembly 20 includes a cap plate 21 coupled with the can 11, ananode terminal 23 insulated from the cap plate 21 by a gasket 22, aninsulating plate 24 on an interior-facing surface of the cap plate 21,and a terminal plate 25 electrically connected to the anode terminal 23.The cathode electrode tap 16 is electrically connected to the cap plate21 and the anode electrode tap 17 is electrically connected to the anodeterminal 23 through the terminal plate 25. Additionally, an electrolyteinjection hole 26 providing a path through which electrolyte may beinjected into the can 11 is formed on the cap plate 21.

FIG. 2A shows an electrolyte injection hole before it has been sealedand FIG. 2B shows an electrolyte injection hole of FIG. 2A after it hasbeen sealed. As illustrated in FIGS. 2A and 2B, the electrolyteinjection hole 26 is formed in the cap plate 21 with a taper 28. Analuminum ball 27 is placed on the taper 28 to seal the electrolyteinjection hole 26 after electrolyte has been injected into the can 11.The ball 27 is compressed into the electrolyte injection hole 26 by apressure device such as a press 1. The ball 27 is welded by the laserwelding to form a weld 29 and seal the electrolyte injection hole 26.

However, the configuration of the taper 28 is such that the ball 27 doesnot always precisely and entirely seal the electrolyte injection hole 26when the ball is pressed into the hole. Accordingly, electrolyte mayleak from the can as indicated by the arrows in FIG. 2B, causingsparking or a potential explosion hazard.

SUMMARY OF THE INVENTION

To achieve the purpose of the present invention according to the oneside of the secondary battery, the electrode assembly in good order of acathode electrode plate, a separator, and an anode electrode plate isincluding; a can including a electrode assembly; a terminal union and anelectrolyte injection hole formed in a cap plate; coupled with anelectrode terminal through the terminal union; the gasket insulated theelectrode terminal with settling between the electrode terminal and thecap plate; and the plug sealed the electrolyte injection hole withpressure to the electrolyte injection hole of cap plate; the peripheryof the plug coated with synthetic material.

By other sides of the secondary battery according to the presentinvention, the secondary battery is including a cathode electrode plate,a separator, and an anode electrode plate; a can including an electrodeassembly and an electrolyte; the electrolyte injection hole formed inthe one side of a cap plate with closing the opened part of the can; andthe plug prevents the electrolyte injection hole of a cap plate;including the film of elasticity material between the plug and theelectrolyte injection hole.

Also, the manufacture method of the secondary battery according to thepresent invention is including the forming step of an electrode assemblycomprising the cathode electrode plate, a separator, and an anodeelectrode plate; the step of the electrode assembly applied to theopened part of a can and the cap assembly including the cap plate formedthe electrolyte injection hole in one side is connecting with the openedpart of a can; the step of forming the film to the electrolyte injectionhole; the step that the electrolyte pour into the inner side of the canthrough the electrolyte injection hole formed the film; and the step ofsealing the electrolyte injection hole by pressing the ball to theelectrolyte injection hole formed the film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a portion of a conventional secondarybattery.

FIGS. 2A and 2B are sectional views of an electrolyte injection hole ofa conventional secondary battery before and after the electrolyteinjection hole is sealed by an aluminum ball, respectively.

FIG. 3 is exploded perspective view of an exemplary embodiment of asecondary battery in accordance with the present invention.

FIG. 4 is a sectional view of an exemplary embodiment of a plug inaccordance with the present invention.

FIG. 5 is a sectional view of a sealed electrolyte injection hole usingthe plug of FIG. 4.

FIG. 6 is a sectional view of a portion of an exemplary secondarybattery in accordance with the present invention.

FIG. 7 is a sectional view of an electrolyte injection hole of thesecondary battery of the FIG. 6.

FIG. 8 is a flow chart of an exemplary manufacturing method of asecondary battery in accordance with the present invention.

FIGS. 9A, 9B, 9C, 9D and 9E are sectional views of an electrolyteinjection hole being sealed by the manufacturing method of FIG. 8.

DETAILED DESCRIPTION

As illustrated in FIG. 3, an exemplary embodiment of a secondary battery30 includes a can 31 housing an electrode assembly 32, and a capassembly 40 sealing the can 31. The can 31 may have a generallyhexahedronal shape and may act as an electrode terminal.

The electrode assembly 32 includes a cathode electrode plate 33, aseparator 34, and an anode electrode plate 35 wound in a jelly-rollconfiguration. Generally, the cathode electrode plate 33 includes analuminum film cathode electrode collector coated on both sides withlithium oxide and the anode electrode plate 34 includes an aluminum filmcoated on both sides with a carbon material.

A cathode electrode tap 37 and an anode electrode tap 36 protrude fromthe cathode electrode plate 33 and the anode electrode plate 35,respectively. The cathode electrode tap 37 and the anode electrode tap36 can be attached to the cathode electrode collector and the anodeelectrode collector, respectively, by welding. Additionally, the cathodeand anode electrode collectors 36, 37 may be wrapped with insulatingtape 38 to prevent a short circuit between the cathode electrode plate33 and the anode electrode plate 35.

The cap assembly 40 includes a cap plate 41, an insulating plate 46attached to an interior-facing surface of the cap plate 41, and aterminal plate 47 attached to an interior-facing surface of theinsulating plate 46.

An anode terminal 45 is inserted through the cap plate 41 and theinsulating plate 46 and is electrically connected to the terminal plate47. A gasket 44 surrounding the anode terminal 45 insulates the anodeterminal from the cap plate 41. An insulating case 48 may be attachedbetween the cap assembly 40 and the electrode assembly 32.

The cathode electrode tap 37 may be attached to the cap plate 41 bywelding, and the anode electrode tap 36 may be electrically coupled tothe anode terminal 45 by being welded to the terminal plate 47. However,the polarity of the electrodes may also be reversed.

An electrolyte injection hole 43 allowing an electrolyte to be injectedinto the can 11 is located on the cap plate 41, the electrolyteinjection hole 43 being sealed by a plug 50. As shown in FIG. 4, theplug 50 may include a ball 51 and a resin 52 coated on the periphery ofthe ball 51. The plug 50 may also have a pin configuration. In oneexemplary embodiment, the ball 51 is made from aluminum, an aluminumalloy, or stainless steel.

In another exemplary embodiment, the resin 52 is fast dry cement resin,and specifically, epoxy resin. The epoxy resin may be mixed with ahardener to provide uniform hardening of the resin. The amount and typeof hardener used may vary resulting in various viscosities, hardeningtemperatures, hardening times of the resin.

The sealing of the electrolyte injection hole 43 by the plug 50 will bedescribed with reference to FIG. 5. The plug 50 is placed onto theelectrolyte injection hole 43 and compressed into the hole. Theperiphery of the plug 50 is laser welded forming a weld 49 adjacent anupper edge of the plug. The resin coated on the periphery of the plug 50rapidly solidifies, seals the plug to the cap plate and helps to form abetter seal between the plug and the cap plate 21, thus preventingelectrolyte from leaking through the electrolyte injection hole 43.

Another exemplary embodiment of a secondary battery of the presentinvention will be described with reference to FIGS. 6 and 7. A secondarybattery 60 includes a can 61 housing an electrode assembly 62, and a capassembly sealing the can. The can 61 may be, for example, aluminum, analuminum alloy, or iron, may be hexahedronally shaped and may act as anelectrode terminal. The cathode electrode plate 63 and the anodeelectrode plate 65 may be substantially similar to the cathode and anodeplates described above.

The separator 64 may be, for example, polyethylene, polypropylene, or acopolymer of polyethylene and polypropylene. In one exemplaryembodiment, the separator 64 may be wider than the cathode electrodeplate 63 and the anode electrode plate 65 to prevent a short circuitbetween the cathode electrode plate 63 and the anode electrode plate 65.

The cap plate 71 may be a flat type having an opening through which theelectrode assembly 62 may be inserted. A gasket 72 may insulate theelectrode terminal 73 from the cap plate 71. An insulating plate 74 maybe attached to an interior-facing surface of the cap plate and aterminal plate 75 may be attached to an interior-facing surface of theinsulating plate 74. The electrode terminal 73 may be electricallycoupled with the terminal plate 75 through an opening in the insulatingplate 74. The cathode electrode tap 66 may be welded to the cap plate 71and the anode electrode tap 67 may be welded to the electrode terminal73. An insulating case 69 may be located between the electrode assembly62 and the cap assembly 60 to insulate the electrode assembly from thecap assembly. In one exemplary embodiment, the insulating case 69 mayinclude a high molecule resin, for example, polypropylene.

An electrolyte injection hole 76 is formed in the cap plate 71 having astepped configuration in which an upper hole portion has a largerdiameter than a lower hole portion. A plug 77 is used to seal theelectrolyte injection hole 76 by being compressed into the electrolyteinjection hole. With reference to FIG. 7, the electrolyte injection hole76 includes a film 78 formed on the upper hole portion, including a stepportion 79. In one exemplary embodiment, the film 78 is formed by dryingresin or a rubber liquid solvent on a surface of the electrolyteinjection hole 76. Exemplary resins may include fluorine resin orpolyolefin resin, and exemplary rubber liquid solvents may includefluorine rubber, butadiend rubber, or Isobutylene-Isoprene rubber.

An exemplary manufacturing method of a secondary battery of the presentinvention is described with reference to FIG. 8. First, the electrodeassembly including the cathode electrode, the separator and the anodeelectrode is formed into a jelly-roll configuration (S1). Then, theelectrode assembly is inserted into the can (S2). The cap plate is thenwelded to the can to seal the can (S3) and electrolyte is injectedthrough the electrolyte injection hole (S4). The electrolyte injectionhole is then sealed with a plug (S5).

The steps described with reference to FIG. 8 are illustrated in moredetail with reference to FIGS. 9A to 9E. As illustrated in FIG. 9A, aloader 80 including a load 82 is prepared and placed adjacent to anupper hole portion of the electrolyte injection hole 76. As illustratedin FIGS. 9B and 9C, the load 82, for example, liquid solvent, is ejectedfrom the loader 80 into the electrolyte injection hole 76 to coat anupper hole portion of the electrolyte injection hole. Next, asillustrated in FIG. 9D, the liquid solvent is dried to form a film onthe upper hole portion of the electrolyte injection hole 76, includingthe step portion 79. After electrolyte has been injected into the can, aball (B) having the same or larger diameter than the electrolyteinjection hole 76 is placed on the electrolyte injection hole andcompressed. As illustrated in 9E, the electrolyte injection hole 76 issealed by compressing the plug into the electrolyte injection hole 76.Accordingly, the method of sealing the electrolyte injection hole 76described above may prevent electrolyte from leaking.

As described above, the secondary battery according to exemplaryembodiments of the present invention allows a sufficient seal to beformed between the plug and the electrolyte injection hole duringwelding of the plug to the cap plate, thus improving the sealingcapability of the plug. Specifically, an elastic film such as resinand/or rubber coated on the plug and/or the electrolyte injection holereduces the likelihood of electrolyte leaking through the plug. Further,use of a resin on the electrolyte injection hole may eliminate the needfor welding the plug to the cap plate, thus increasing the manufacturingefficiency of the secondary battery.

The present invention is not limited to the exemplary embodimentdescribed herein. Rather, modifications apparent to one of skill in theart may be made within the scope of the invention claimed in theappended claims.

1. A secondary battery comprising; an electrode assembly; a can havingan opening at one end of the can, the can housing the electrodeassembly; a cap plate sealing the opening, the cap plate having anelectrolyte injection hole for inserting electrolyte into the can; anelectrode terminal coupled to the cap plate to provide an electricalconnection between the electrode terminal and the electrode assembly; agasket located between the electrode terminal and the cap plate forinsulating the electrode terminal from the cap plate; and a plug forsealing the electrolyte injection hole, the plug being coated with anelastic film.
 2. The secondary battery of claim 1, wherein the elasticfilm is a resin.
 3. The secondary battery of claim 2, wherein the resinis a hardening resin.
 4. The secondary battery of claim 3, wherein thehardening resin is an epoxy resin.
 5. The secondary battery of claim 1,wherein the plug is a ball or a pin.
 6. The secondary battery of claim5, wherein, the plug is made from material selected from the group ofaluminum, aluminum alloy, and stainless steel.
 7. A secondary batterycomprising; an electrode assembly; a can having an opening at one end ofthe can, the can housing the electrode assembly; a cap plate for sealingthe opening, the cap plate including an electrolyte injection hole forinserting electrolyte into the can; and a plug for sealing theelectrolyte injection hole; wherein an elastic film is located betweenthe electrolyte injection hole and the plug.
 8. The secondary battery ofclaim 7, wherein the electrolyte injection hole has a steppedconfiguration such that an upper hole portion of the steppedconfiguration for inputting electrolyte into the can has a diameterlarger than a diameter of a lower hole portion adjacent to the upperhole portion; and wherein the elastic film coats wall surfaces of theupper hole portion.
 9. The secondary battery of claim 7, wherein theelastic film is fluorine resin or polyolefin resin.
 10. The secondarybattery of claim 7, wherein the elastic film is fluorine rubber,Butadiend rubber, or Isobutylene-Isoprene rubber.
 11. A method ofmanufacturing a secondary battery, the secondary battery including a canhaving an opening at one end of the can, the method comprising;providing an electrode assembly; inserting the electrode assembly intothe can through the opening; sealing the opening with a cap plate, thecap plate having an electrolyte injection hole for inserting electrolyteinto the can, coating the electrolyte injection hole with an elasticfilm; injecting electrolyte into the can through the electrolyteinjection hole; and compressing a plug to seal the electrolyte injectionhole such that the plug contacts the elastic film.
 12. The method ofclaim 11, wherein the electrolyte injection hole further comprises astepped configuration such that an upper hole portion of the steppedconfiguration for inputting electrolyte into the can has a diameterlarger than a diameter of a lower hole portion adjacent to the upperhole portion, and wherein coating the electrolyte injection hole with anelastic film further comprises: preparing a loader with a liquidsolvent; aiming the loader at the upper hole portion; injecting theliquid solvent into the upper hole portion while moving the loader alonga diameter of the electrolyte injection hole; and drying the liquidsolvent to form the elastic film.
 13. A method of manufacturing asecondary battery, the secondary battery including a can having anopening at one end of the can, the method comprising; providing anelectrode assembly; inserting the electrode assembly into the canthrough the opening; sealing the opening with a cap plate, the cap platehaving an electrolyte injection hole for inserting electrolyte into thecan, injecting electrolyte into the can through the electrolyteinjection hole; and compressing a plug to seal the electrolyte injectionhole; wherein the plug includes a resin covering the surface of theplug.
 14. The method of claim 13, wherein the resin is a hardeningresin.
 15. The method of claim 14, wherein the hardening resin is anepoxy resin.
 16. The method of claim 13, wherein the plug is made frommaterial selected from the group of aluminum, aluminum alloy andstainless steel.